TEHRAN, May 18 (Xinhua) -- The Iranians will decide on their country's international relations and foreign policy by their vote on the presidential election on Friday, an Iranian political expert said on Thursday.

"Obviously, if President Rouhani is reelected, it would be very much the same (foreign) policies that we have observed during the past three and half years," Sadeq Zibakalam, professor of political science of Tehran University, told Xinhua.

"However, if the radical contestant of him, Mr. Raisi, wins, it would be a step backward," said Zibakalam.

"Since his (Raisi's) power base comes from the hardliners, it will be projected in his foreign policies," he said.

Iran's political landscape has been dramatically polarized over the country's key issues raised in the recent debates between the two major presidential hopefuls, namely the incumbent moderate President Hassan Rouhani and his conservative rival Ebrahim Raisi.

Rouhani believes in detente with the West and even with the United States, and he has, to some extent, achieved this, Zibakalam said, adding that "he will try to maintain good and warm relations with many other countries if he is reelected."

"If the hardliners win, then they will put the clock back. They will forget about friendly approach with regard to some countries. They will even go back to anti-U.S. slogans, calling for the destruction of Israel," said Zibakalam.

Besides, "it is very likely that nuclear deal would be damaged," he warned.

"At the moment, we know that (the U.S. President Donald) Trump wants to get rid of it, but he cannot, because Iran has not violated the deal ... and it has done all its obligations," the expert said.

Iran and six world powers, including Britain, China, France, Germany, Russiaand the United States, reached an agreement on the Iranian nuclear issue in July 2015 that put it on the path of sanctions relief, but with more strict limits on nuclear program.

"Presently, if the United States wants to derail the deal, other parties of the deal will not follow it," said Zibakalam.

However, if Raisi is chosen, because of "his anti-Americanism, because of his anti-westernism, the ties with the United States will further suffer" and Iran may even lose the support of other parties involved in the deal, the expert said.

In the TV debate on May 2, Raisi said that all the parties involved in the nuclear deal should respect it.

However, he criticized President Rouhani for what he called "failure in making the West to remove all anti-Iran sanctions after the implementation of the deal."

He said that Rouhani has also failed to end Iran's economic recession and remove all banking sanctions.

As for Iran's regional policies, the Iranian expert said that "Raisi won't do much about the normalization of ties with Saudi Arabia, and at least will not create a condition that the animosity between Riyadh and Tehran not to increase."

Iran and Saudi Arabia are at loggerheads over their expansion of influence in Iraq, Syria, Yeman and Bahrain.

The Iranian Foreign Ministry announced on Monday that the Islamic republic does not seek any "tension" with Saudi Arabia.

However, "we will see more Iranian involvement in Yemen, and more Iranian involvement in Syria issues, if Mr. Rraisi is elected," Zibakalam concluded.